Initial Corrosion Behavior of Dual-Phase Bronze with Tin Segregation in Weakly Alkaline Soil Environment

The corrosion behavior and mechanism of alpha phase and delta phase of a dual-phase bronze alloy with tin segregation in a weakly alkaline archeological soil environment (Xi'an, China) for one year were studied. The element distribution and phase composition in the bronze substrate were analyzed by metallographic microscopy, XRD and EPMA. The corrosion products, cross-sectional micromorphology, corrosion weight loss and electrochemical tests were performed on the samples after the test. The results showed that the bronze substrate was composed of alpha(I) and (delta + alpha(II)) eutectoid, and alpha(I) was segregated. During the corrosion process, the surface of the sample first turned reddish brown at the beginning of the corrosion process and gradually turned into dark green with days. The corrosion tendency inside the substrate was alpha phase segregation > alpha phase branches > delta phase. In the early burial stage, the corrosion products were mainly Cu2O, Cu-2(OH)(2)CO3, Cu-2(OH)(3)Cl, SnO2 and PbO. The corrosion products were mainly Cu-2(OH)(3)Cl and PbCO3 in the later burial stage. The DFT calculation was used to study the crucial role of O-2 in the soil corrosion of segregation dual-phase alloy, and its corrosion mechanism in weakly alkaline soil environment was explained.